I got a Samsung Series 3, comes with an A8 4500m and the 7670m.
If you want a game performance, I run Battlefield 3 in windowed mode on windows 8 at about 30-45 FPS, on Low Graphics Preset. Although, the performance has gone to the dogs since going back to Windows 7.
As a Laptop, Lenovo has slightly suprior builds and the Driver Support is good (Got 3 Lenovo Lappys in the family, 1 Thinkpad and 2 Ideapads, and a ThinkPad Tablet 1.) Not so sure about Dell, but personally I don't enjoy the astetic looks of the Dell laptop ranges. To boxy and generic for my liking.
Anyway, there were my 2 cents worth.